Neutron diffraction study of the monoclinic – tetragonal phase transition in NdNbO<sub>4</sub> and NdTaO<sub>4</sub>
Matilde Saura‐Múzquiz, Bryce G. Mullens, Helen E. Maynard‐Casely, Brendan J. Kennedy
Abstract
, the thermal evolution of the lattice parameters and symmetry modes suggest the transition is continuous, although a small discontinuity in both the spontaneous strains and symmetry distortion modes shows the transition is strictly first order. Analysis of the refined structures reveals that the Nb and Ta cations are best described as having a distorted 6-coordinate arrangement in the monoclinic structure, with four short and two long bonds. Breaking of the two long bonds at high temperatures, resulting in a transformation of the Nb(Ta) coordination to a regular tetrahedron, is believed to be responsible for the first order nature of the transition.
Topics & Concepts
Monoclinic crystal systemTetragonal crystal systemNeutron diffractionPhase transitionCrystallographyPhase (matter)Materials scienceDiffractionChemistryCondensed matter physicsCrystal structurePhysicsOpticsOrganic chemistryFerroelectric and Piezoelectric MaterialsNuclear materials and radiation effectsMicrowave Dielectric Ceramics Synthesis